Dose reduction via dynamic collimation adjustment for targeted field of view and/or digital tilt CT

Abstract

Among other things, one or more systems and/or techniques are described for dynamically adjusting, in a fan-angle direction, attenuation of radiation during an examination of an object such that portions of the object that are not represented in resulting (tilted/targeted) images of the object are exposed to less radiation than portions of the object that are represented in resulting (tilted/targeted) images of the object. As a rotating gantry is rotated, blades of a pre-object collimator are dynamically repositioned to selectively attenuate emitted radiation. A collimator adjustment component may be configured to determine how to reposition the blades based at least in part upon at least one of a desired tilt of the resulting (tilted) image(s), a translational position of the object, and a gantry rotation angle, for example.

What is claimed is: 
     
       1. A computed tomography (CT) imaging modality, comprising:
 an ionizing radiation source configured to emit ionizing radiation, the ionizing radiation comprising at least one of x-ray radiation or gamma radiation; 
 a detector array configured to detect at least some of the ionizing radiation; and 
 a pre-object collimator configured to dynamically adjust, in a fan-angle direction, attenuation of the ionizing radiation during an examination of an object as a function of an effective digital tilt of the CT imaging modality, the effective digital tilt corresponding to a specified tilt angle of a tilted image slice relative to a rotational plane of at least one of the ionizing radiation source or the detector array. 
 
     
     
       2. The CT imaging modality of  claim 1 , the pre-object collimator comprising a region of substantially no attenuation and a region of attenuation. 
     
     
       3. The CT imaging modality of  claim 2 , the pre-object collimator configured to dynamically adjust attenuation of the ionizing radiation by dynamically adjusting a size of the region of substantially no attenuation. 
     
     
       4. The CT imaging modality of  claim 3 , the region of attenuation comprising one or more blades. 
     
     
       5. The CT imaging modality of  claim 4 , a blade of the one or more blades configured to be dynamically repositioned during a rotation of at least one of the ionizing radiation source and the detector array to dynamically adjust the attenuation of the ionizing radiation. 
     
     
       6. The CT imaging modality of  claim 2 , the region of attenuation configured to attenuate less than all of the ionizing radiation traversing the region of attenuation. 
     
     
       7. The CT imaging modality of  claim 1 , the pre-object collimator comprising one or more blades configured to adjust attenuation of the ionizing radiation in the fan-angle direction. 
     
     
       8. The CT imaging modality of  claim 7 , a blade of the one or more blades comprising a material configured to attenuate less than one-hundred percent of the ionizing radiation impinging upon the blade. 
     
     
       9. The CT imaging modality of  claim 7 , comprising a collimator adjustment component configured to cause a blade of the one or more blades to be dynamically repositioned during rotation of at least one of the ionizing radiation source or the detector array as a function of a trajectory of the ionizing radiation relative to the object. 
     
     
       10. The CT imaging modality of  claim 1 , comprising an image reconstructor configured to generate the tilted image slice, and the pre-object collimator configured to dynamically adjust attenuation of the ionizing radiation in the fan-angle direction as a function of detector cells utilized to generate the tilted image slice. 
     
     
       11. The CT imaging modality of  claim 1 , the CT imaging modality not configured to mechanically tilt. 
     
     
       12. A method for imaging an object, comprising:
 dynamically adjusting attenuation of an ionizing fan beam via a pre-object collimator during an examination of an object from which a tilted image slice of the object is generated as a function of an effective digital tilt corresponding to a specified tilt angle of the tilted image slice, the ionizing fan beam comprising at least one of an x-ray fan beam or a gamma-ray fan beam. 
 
     
     
       13. The method of  claim 12 , comprising rotating at least one of an ionizing radiation source or a detector array about the object during the examination, and the dynamically adjusting attenuation of an ionizing fan beam comprising dynamically adjusting attenuation of the ionizing fan beam while rotating the at least one of the ionizing radiation source or the detector array. 
     
     
       14. The method of  claim 12 , the dynamically adjusting attenuation of an ionizing fan beam comprising dynamically adjusting attenuation of the ionizing fan beam as a function of a position of an ionizing radiation source relative to the object. 
     
     
       15. The method of  claim 12 , comprising identifying one or more cells of a detector array from which generated information is not used to reconstruct the tilted image slice, and the dynamically adjusting attenuation of an ionizing fan beam comprising adjusting attenuation of the ionizing fan beam such that ionizing radiation of the ionizing fan beam that would impinge the one or more cells is attenuated by the pre-object collimator. 
     
     
       16. The method of  claim 12 , the dynamically adjusting attenuation of an ionizing fan beam comprising dynamically adjusting attenuation of the ionizing fan beam as a function of a z-position of the object. 
     
     
       17. The method of  claim 12 , the dynamically adjusting attenuation of an ionizing fan beam comprising:
 dynamically adjusting a fan-angle direction of a region of substantially no attenuation in a pre-object collimator; and 
 dynamically adjusting a fan-angle direction of a region of attenuation in the pre-object collimator. 
 
     
     
       18. The method of  claim 17 , at least a portion of the ionizing fan beam traversing the region of attenuation being detected by a detector array. 
     
     
       19. A non-transitory computer readable medium comprising computer executable instructions that when executed perform a method, the method comprising:
 rotating a gantry comprising an ionizing radiation source and a detector array about an object during an examination of the object, the ionizing radiation source comprising at least one of an x-ray source or gamma source; and 
 dynamically adjusting via a pre-object collimator, in a fan-angle direction, attenuation of ionizing radiation emitted by the ionizing radiation source while rotating the gantry to vary an amount of the ionizing radiation to which the object is exposed, the dynamically adjusting a function of an effective digital tilt corresponding to a specified tilt angle of a tilted image slice relative to a rotational plane of the gantry. 
 
     
     
       20. The non-transitory computer readable medium of  claim 19 , the dynamically adjusting attenuation of the ionizing radiation comprising dynamically adjusting attenuation of the ionizing radiation as a function of a position of the ionizing radiation source relative to the object.